The disclosure herein relates to a method for coating a substrate with a lacquer and to a device for planarising a lacquer layer on a substrate.
Micro- and nano-fabrication processes typically use lacquers which are applied in a layer onto the substrate to be processed. With the aid of these lacquers it is possible to produce e.g. masks on the substrates, with the aid of which a desired structure can be produced or processing can be effected on the substrate. For this purpose, the lacquers are e.g. light-sensitive so that the desired structure can be transmitted from a photo-mask to the light-sensitive lacquer with the aid of optical imaging.
In order to achieve optimum results, it is extremely important that the applied lacquer layer is free of any irregularities and particles. In addition to rotation methods, spraying methods are also used for applying the lacquer onto the substrate, in which spraying methods the lacquer is sprayed onto the substrate by means of a nozzle. Particularly in the case of substrates having topographies, i.e. substrates which themselves already have vertical, three-dimensional structures on their surface, the most homogeneous possible lacquer layer can be achieved in an economical manner only by spraying-on the lacquer.
However, when the lacquer is sprayed on, lacquer particles form on the lacquer layer, as a certain number of lacquer drops dry in flight between the nozzle and the substrate and then impinge already as (almost) cured lacquer particles upon the surface of the substrate or the lacquer present at this location. These lacquer particles collect on the sprayed-on lacquer layer and lead to problems during further processing, e.g. during exposure to light, and ultimately lead to local defects on the structures produced.